This invention relates to a method for weaving, as well as to a device for driving weaving frames during the implementation of the aforementioned method.
The invention more especially relates to a method of the type whereby in each weaving cycle a number of weaving frames are held in a same extreme position, while all remaining weaving frames are moved.
Of the fabrics which are produced in this manner denim is the most common during the weaving of so-called blue jeans, for example blue warp threads are utilized and white weft threads are woven in. A so-called three/one weave is formed. This means that weaving is performed with one or more sets of four weaving frames, whereby with each shed change of each set, two weaving frames remain above the warp one weaving frame moves upward from below, and one weaving frame moves downward from above. With a completely open shed, therefore, three weaving frames are always in their highest position, while the fourth weaving frame is in its lowest position.
In order to obtain a good quality, or blue color in the case of blue jeans, it is known that at the moment of the beating up, the tension in the bottom warp threads should be greater than in the top warp threads.
It is also known that, in order to achieve a tension in the bottom warp threads is greater than the tension in the top warp threads, the guide for the start of the weaving shed should be brought up out of its normal position, this guide being either the back rest or a guide especially provided for this purpose, so that the top warp threads between the start and the end of the weaving shed have to travel a shorter course than the bottom warp threads.
The aforementioned technique of weaving, whereby the back rest or any other guide at the start of the weaving shed is placed upward out of its normal position, has however the disadvantage that when restarting the weaving machine after a machine stoppage starting stripes are sometimes formed, especially in the case where weaving is effected with closely beaten up weft threads and when the weaving machine has stood idle for relatively long.